Safety device for instrument approach systems



Sept 29, 1953 c. c. PINE Erm.

SAFETY DEVICE FOR INSTRUMENT APPROACH SYSTEMS Filed Feb. 17, 1950 Y i THEIR ATTORNEY w mv l-Illu Patented Sept. 29, 1953 SAFETY DEVICE FOR INSTRUMENT APPROACH SYSTEMS Cecil C.`Pine, Lake Ronkonkoma, and Charles L. Sharp, Setauket, N. Y., assignors to The Sperry Corporation,A a corporation of Delaware Application February 17, 1950, Serial No. 144,834

Patent No. 2,613,350 issued October 7, 1952, andv Seria] No. 128,227 for Control Systems, filed November 18, 1949, now Patent No. 2,613,352. is-

sued October '7, 1952, both assigned to the assignee of the present application. According to this system, the two pointers of thel indicator for off course and out of trim are combined ona single face or dial and both normally read Zero, so that all the aviator need do is to keep the course and pitch pointers on the indicator at the zero or normal position to bring the craft in for a smooth landing.

As explained in the aforesaid applications, this instrument may also be used during normal flight and for this purpose a selector switch is provided for the different uses of the instrument under different conditions. The present invention concerns only the blind landing operation, so that the present disclosure will be confined to this use of the instrument in or immediately following this operation.

When making an instrumentl approach, it often happens that at the last minute, the aviator finds that he cannot land on the landing strip selected and it is therefore necessary at times just before the touchdown is'reached to abandon vhis intention to land and instead to y up and perhaps go around for another appreach.

When this happens the pilot must cease coming down the glide path vand must imf mediately trim the aircraft to a greater angleY of attack and preferably also gun theengine to climb away from the field and avoid obstacles beyond the runway. Since the pilot has been relying upon his zero reading indicator up to that point, it would be very helpful tothe pilot if he could continue to rely on the same instruflight vindicator which when'thrown will severthe lindicator input fromthe' glide path guidance beam signal, at least, thereby discontin- 12 cmims. (Cl. 343-108) r2 uing the descent signal and preferably also showlng a y up signal. At this time the signal from the localizer beam may also be severed or preferably modified so that although the localizer beam may continue to be followed, the course indicatingV pointer will not be disturbed by close approach of the aircraft to the localizer transmitter, and excessive bank angles avoided.

Referring to the drawings,

Fig. l is a schematic view showing how our go around switch may be used when the zero reading indicator is being used in instrument approach operation;

Fig. 2' shows a convenient location for the switch on the engine throttle, so that pressing of the, switch'button may be made simultaneous With the increased engine throttle; and

Fig. 3 shows the selector switch usually used in VVconnection with the known Zero reading guidance system to which v this invention relates.

As explained in .the .aforesaid applications, during radio guided approaches, the output of the radio glide path receiver I after passing through `the modulator 2 is led to a mixer amplifier and rectifier 3 where this signal is combined withl the stabilizing pitch signal from the gyro-vertical 4. Thev pitch signal is represented as generated by a synchro 5 on the pitch axis of gyro 4,' which produces a signal proportional in amount to the departure of the craft from a level or trim position and reversible in phase when such departure is up or down. The combined A.Y C. signal is amplified and rectified and the output led to the Zero reading indicator 6 thereby causing movement of the horizontal pointer 1 up or down from its zero or `central position, according to whether the aircraft needs trimming up or down to keep it on the glide path.

As explained in the aforesaid applications, it is characteristic of this type of meter that it read zero not only when the aircraft is flying on the glide path (or level), but also when the aircraft has departed from, the glide path as soon as itstrim has been changed proportionate to the amount of departure to bring the aircraft 'smoothly back into `the glide path.

Similarly, the output of the localizer receiver 8 is led through a modulator 9 and to a mixer amplifier 'and 'rectifier I0 where the signal is combined with 'two otherV signals, one a course signal"from"the synchroV I l operated lfrom the compass vI2 and the other a signal from the synchro i3 operated from the bank axis of the gyro-vertical 4. The combined output of the 3 three signals is fed to the indicator 6 to cause lateral movement of the pointer I 4 to the right or left from its normal or zero position. ,As with the case of the pointer 1, the pointer I4 will read zero not only when the `craft is on the 5 radio course, but also if off course when the craft is banked at a proportional angle proportionater to-conrse departure tolcauser-the'l-craft to return smoothlyto its radio cou-rsei According to our invention, We provide an emergency switch or push button I5 which theev aviator may press or throw, in case liedesires not to land when approaching thetouclidcwriLv point, but decides to go around again. I'hep'ress-` ing of push button I5, it willbe-fseemswill." evenfc the output of the glide path'smodulatrrI romfi the mixer rectifier 3 thus leaving thesigfiaifrb'nrli the attitude gyro in sole controlto erase the.. downward glide signal. As shown the aforesaid prior application Serial No. 128,227 oSpen- 26%1 cer Kellogg, a biasing signalil 02 may be supplied to the glide path-.signal-whenever. theselector switch@ Zit-V30 is thrown. cioekwise into the approach.: positiorlif-so .that the aircraft need .no-t. Ily above the barrn .if otherwise necessary to obtainv a-Asig.- -25 nal balancingthat-from the attitude gyrowhen flying down the glide path. ,In-.such case, switch l 5 of this-application-in. severing the output. -fromthe glide .path receiver would likewise sever-the aforesaid biasing means.-Atlthegsametimefwe 3o modify the lgyro signaljf to'fcall. -for .a-. climb, by` throwing-ln anotherbiasing -means-r such Aas* a signal .froma synchro Idfwhich isfgiven-apredetermined displacement from. knoblll I Isofas toset inra predetermined-pitchsignal intov the mixer; thus causing', theindicator i Jno1-immediately callV v for aclimbat a-safe angle.. A s'therenginespeed should be". increased simultaneously,VV we-.f havev shown- .the .button-y as y.convenientlyplaced on the enginethrottle lil- (li'igi4 2),sothat the'itwo-.Operations -maybekaccoinplished as one.

The saine button I5 also preferably either.i breaks .the :circuit .from-.- the localizer-modulator or lmodifies the signalIk therefrom-td,preventVY erratic .operation of the meteras-thevcraft closely. 4-5 approaches-.the localizer transmitter.- Pressingel the button, therefore; alsoiirst opensthebridging contact- 35 in- Vthe Acircuit between modulator-v 9 andthe-receiver -Ili'and-.closes a circuitbetweenl; contacts CB and 1 3' thereby placingla signal-.limiter ."50 in the-shapeof acvariableresistor.IS-in the-circuit designed. to Vlimit anylvbank angleindication to amaximum'jof about. 1 0 .degrees-sof that =excessivebanks will lbe.avoide:l .-whilethe lcraft :is-f? near-the ground..` Thebuttonfalso .shown :as-:55 havingv a .thi-rdcontactorl which throws-finto` the-circuit-a-device 25 for-reducing thefamplitude; of thej signals .fron1. thelocalizer :receiver as theV transmitter is beingfapproached- Suchany opera-1 tionis termed inthe art course -softeningand-is" described-in thepatentto T.. M; Ferrill-,f' Jr., No.5 2,439,044; dated April 6, 1948- for Course-SofteningSystemsy assigned .to -the assignee of` the pres f ent invention..-y A third .position of'the switch is i shown .in which the= localizerf: receiveris" com-65 pletel-y disconnected. Under such condition, the I craft willY still bekept oncourse-'by -fo1lowing1 the zero reading indicatonandif course changes fare desired. the .synchro I Il v'could 'be-.adjusted .fromi' the knobzl. v

As soon =as-the craft-issafelyjaway fronritheV landing .field 'the pilot,v :by .operating `hisfselector switchjv 3D, (sho-wn in' 'more detailinthe-second of the aforesaid-Kelloggapplications) may-rev" sume the flight system. desired by restoringl switch 75 4 I5 to its normal position and by moving the course selector handle 3l to the flight instru-- ment position for regular cross country night o-r to the ODR position for radio guided cross coun-- try night or resume the approach position, in' which case, by following the indicator 6, the pilot will again cause the craft to approach and reach a :ianriin'gpesitiohtover tlf ll'ndirigf field runway, allf-as'moreflly describ'din 1the aforesaid Kellogg applications.

A's many changes could be made in the above construction andmany apparently widely differenibembodiments of this invention could be made without departing from the scope thereof, it is intended thatrallrnattr contained in the above .des'eril'zititin`V rfshown-in the accompanying drawingsfifsha-llfbeiirtrpreted as illustrative and not in a .limiting sense. f. Y

Thus our invention is not limited to the use of affvisiialliiight indicator such as a zero reading cross pointer meter, lbut is also applicable for-fuse?.-in-an-.airplane equipped with an automatie-.pilotHhavingeairadio= approach @system in. which-.fthe I :radio-glide L path; land localizer beams operate= through..thewautomatic pilot for automatic-*approach and-landingg-such as disclosed in thegpatents fto=r.F.., Lil-.Moseleyvr Nos; 2 ,423,336 and 2,423,3.377 dated July-f1, 1947'for RadiofControlled Pilot System. :In other'words, thecourse or 'azimoth-guidancesignals generated in" applicants mixerqamplier-and-rectifier:I 0 and the guidance signalsifforL trim orl pitch-generated in applicants mixer amplifier-YandreCtieriS'may betused as signals-.tooperatefthefcrafts aileron and elevator.- servo. motors respectively, .i instead of operatinge. such-.i control 1- surfaces through the-` intermediaryMathe-.humanV pilot `.who vobserves and.

followsl theyzero reading-indicator 6: We, thereadapted for either-.methodfof approach, that is, through a human pilot or through-an automatic pilot,-jfthe compound .guidance signals being substantiallvthesame :in-both=inst`ances,-but in one case operatingfavisual. indicator and in the other.

the serves off-theautomaticipilot". Specic claims to thelatter System-are-'reserved-for a companionY Slgna path;

to signals-.produced by.v both said receiver and saidattitude instrumentpnormally idle means for' biasingethe` :signalfrom "said instrument to call for -enclimbsa-t a= predetermined angle, and manually. operablev4 means-for renderingzsaid guidance means responsive-only tothe signal' from the attitude instrument.biasedf'from'said biasing means.

2.- In. a.radio approach Asystem for instrument landingghaving iglide path.` and localizer receivers;A

meansgfor .generating-1 a trim- :or pitch' guidance signalandacourse .guidance-signal, course, pitchv and bankattitude maintaining instruments, guidance means normally responsive as to pitch -tol signalsproduced-.by fboth. lsaid` glide path-f receiverl and; the p i-tch.- attitude of said.' attitude instrument,a nd asto course'from-fsaid localizer re'- ceiv'er! .the'bankv :attitude of.l said' attitude'in'strument and lsaid coursefinstrument. and manually" 1 upon.departureofithe'craft frcmthe glide an rattitude maintaining instrument havingfmeans.` producing pitch-signals .upon1 pitchl or r climb -ofthecraftt a'guidance'means responsive Y operable means for rendering said guidance signal responsive in pitch only to said attitude instrument and in course only to said course instrument and the bank attitude of said attitude instrument.

3. In a radio approach system for instrument landing having a glide path receiver adapted to produce lpitch signals upon departure from the glide path, an indicator of the Zero reading type, an attitude maintaining instrument adapted to produce signals upon change of pitch attitude, said indicator being normally responsive to pitch signals produced by both said receiver and said attitude instrument, and manually operable means for rendering said indicator responsive only to said attitude instrument.

4. A radio approach system for instrument landing as claime-d in claim 3, having means for biasing one of said signals during landing approach1 whereby the indicator reads zero when the craft is flying directly down the beam.

5. In a radio approach system for instrument landing having a glide path receiver, an indicator of the zero reading type, an attitude maintaining instrument, said indicator being responsive to signals produced by both said receiver and said attitude instrument, normally idle means for biasing the signal from said instrument to call for a climb at a predetermined angle, and

manually operable means for rendering said indicator responsive only to the signal from the attitude instrument biased from said biasing means.

6. In a radio approach system for instrument landing having glide path and localizer receivers,

an indicator of the cross pointer type, course, and pitch and bank attitude, maintaining instruments, said indicator being normally responsive as to pitch to signals produced by both said glide path receiver and the pitch attitude of said attitude instrument, and as to course from said localizer receiver, the bank attitude of said attitude instrument and said course instrument, and manually operable means for rendering said indicator responsive in pitch only to said attitude instrument and in course only to said course instrument and the bank attitude of said attitude instrument.

7. A radio approach system as claimed in claim 6, having normally idle means for biasing the l pitch signal from said attitude instrument to `call for a climb at a predetermined angle, said means being brought into action upon operation of the manually operable means of claim 6.

8. A radio approach system for blind landing having glide path and localizer receivers, an indicator of the Zero reading type, course and pitch and bank attitude maintaining instruments, said indicator being normally responsive as to pitch Ver 6 to said signals produced by both said glide path receiver and the pitch attitude of said attitude instrument, and as to course from said localizer receiver, the bank attitude of said attitude instrument and said course instrument, normal idle means for biasing the pitch signal from said attitude instrument to call for a climb, and manually operable means for rendering said indicator responsive only to said biasing means and attitude instrument.

9. A radio approach system as claimed in claim 8, in which said manual means also modiiies the effective localizer signals to limit the bank angle indicated thereon.

10. A radio approach system as claimed in claim 8, in which said manual means also modies the effective signals to reduce their volume as the localizer transmitter is approached.

11. A radio approach system for blind landing having glide path and localizer receivers, an indicator of the zero reading type, course and pitch and bank attitude maintaining instruments, said indicator being normally responsive as to pitch to said signals produced by both said glide path receiver and the pitch attitude of said attitude instrument, and as to course from said localizer receiver and the bank attitude of said attitude instrument, normal idle means for biasing the pitch signal from said attitude instrument t0 call for a climb, and manually operable means for rendering said indicator responsive only to said biasing means and attitude instrument.

12. In a radio approach system for instrument landing having a glide path receiver producing a signal upon departure of the craft from the glide path, an attitude maintaining instrument having means producing pitch signals upon pitch or climb of the craft, a guidance means responsive to signals produced by both said receiver and said attitude instrument, normally idle means for biasing thev signal from said instrument to call for a climb at a predetermined angle, and means for severing the radio receiver signal from the guidance means and transferring the same to said biasing means whereby a fly up signal from the attitude instrument is transmitted.

CECIL C. PINE. CHARLES L. SHARP.

References Cited in the ille of this patent UNITED STATES PATENTS Number Name Date 2,372,185 Wittkuhns Mar. 27, 1945 l FOREIGN PATENTS Number Country Date 516,567 Great Britain Jan. 5, 1940 888,812 France Sept. 13, 1943 

